1. Field of the Invention
The present invention relates generally to the treatment of water from coal-bed-methane (hereinafter “CBM”) wells and, more particularly, to a CBM water treatment system which utilizes aqueous sulfurous acid produced by a solid sulfur-based sulfurous generator to treat the CBM water and an injection system to further treat the CBM water by increasing the level of calcium in the CBM water.
2. Description of the Prior Art
CBM wells are being developed in increasing numbers throughout the United States and other parts of the world. These wells are drilled into coal seams to withdraw ground water to reduce the hydrostatic pressure on the coal seam. The reduced pressure allows methane gas to migrate to the well bore where it moves to the surface and is collected. Where possible, operators prefer to discharge the produced water into nearby streams, rivers, or other surface water bodies. Depending on the chemical characteristics of the produced water, different levels of treatment are applied to the produced water before discharge. In some locations, produced water cannot be discharged and is injected, reused, or evaporated.
Problematic CBM water typically has an elevated pH and high levels of bicarbonates and sodium. It is not unusual to find CMB water with 300–2000 PPM of bicarbonates and 200–600 PPM of sodium. Water with these characteristics is detrimental to soil, crops and turf. High bicarbonate/high sodium water plugs soil pore spaces and prevents adequate moisture and nutrients from reaching the root structure of crops and grasses.
With water resources in the United States and other parts of the world becoming more scarce, an important environmental challenge is to economically treat and utilize problematic CBM. The most common method that is currently utilized is to irrigate land with CBM water and subsequently spread sulfur and gypsum on the land in an attempt to counteract the deleterious effects of bicarbonates and sodium.
This methodology has several drawbacks. It is difficult spread gypsum and sulfur to irrigated land in a uniform, consistent, and cost-effective basis, especially during austere weather conditions. Moreover, it is doubtful that this methodology effectively resolves the problems associated with high bicarbonates and sodium. Spreading sulfur on land that is irrigated with high bicarbonate water may do little to reduce the level of bicarbonates in soil on a consistent basis. Although much research supports the use of gypsum in leaching sodium through the soil profile, the benefit of gypsum is greatly lessened when high levels of bicarbonates are present. Adding calcium via gypsum to soil being irrigated with high-bicarbonate or high-carbonate water can create calcium carbonate. Not only does calcium carbonate further aggravate soil problems, but less calcium is available to displace sodium.
Thus, there remains a need for a new and improved methodology for treating CBM water, which utilizes aqueous sulfurous acid produced by a solid sulfur-based sulfurous generator to treat CBM water and an injection system that further treats CBM water by increasing the amount of calcium in CBM water, while, at the same time, includes a shut-off safety system to prevent leakage of molten sulfur from the sulfurous generator.